Starting a Solo Business in Belgium: What Nobody Tells You About the Eenmanszaak

There's a moment every developer who's done enough freelance work eventually reaches: you've had the third client in a year pay you via a personal bank transfer, your accountant friend has told you three times that you need to get structured, and you've started googling "zelfstandige worden belgie" late at night. That's the moment. You're going independent.

I had that moment a few years ago. I knew roughly what I wanted. Consult for clients, build my own products, and have a legal entity behind it all. What I didn't know was how much friction stood between that idea and a working business registration in Belgium.

This is the guide I wish I'd had.

What Is an Eenmanszaak?

An eenmanszaak (Dutch) or entreprise individuelle (French) is a sole proprietorship, the simplest legal structure for independent work in Belgium. There's no separate legal entity: the business is you. Your personal and business assets are legally merged (this matters for liability, more on that later).

The key identifiers you'll work with:

KBO number (Kruispuntbank van Ondernemingen): your unique business identifier, like a company registration number. Everything official flows through this.
BTW/TVA number: your VAT number, in the format BE + 10 digits. You need this to invoice clients for services.
Rijksregisternummer: your national registry number, linked to your identity card. This is how the state knows who's behind the business.

You don't incorporate, you don't create a new legal entity, and you don't need a notary. That's both the advantage and the limitation.

The Registration Process

Here's the actual process, step by step:

Choose an ondernemingsloket. These are accredited business registration offices (like Liantis, Acerta, UCM, NSZ). They handle your KBO registration. Some are faster than others. I used Liantis and had my KBO number within 24 hours.
Register your activity codes (NACE codes). These describe what your business does. Developers typically register under software development, IT consulting, and sometimes e-commerce if you're selling products. Get these right the first time; changing them costs time.
Activate your BTW number. Done through your ondernemingsloket at the same time as KBO registration, or separately via My E-Gov. You'll choose between quarterly and monthly VAT declaration. Quarterly is standard for smaller operations.
Join a social insurance fund (sociaal verzekeringsfonds). Mandatory within 90 days of starting. Options include Liantis, Acerta, Xerius, SNI, and others. They collect your social contributions quarterly. Choose one and go, they're largely equivalent for a standard eenmanszaak.
Open a separate business bank account. Technically not legally required for an eenmanszaak, but practically essential. Mixing personal and business finances is a nightmare for accounting. KBC, BNP Paribas Fortis, Belfius, and the challenger banks (Finom, Qonto) all offer business accounts. Qonto worked well for me. Fast setup, good API for accounting integrations.

The whole process takes about one to two weeks if you have everything ready. The bottleneck is usually waiting for correspondence from the social fund and the BTW activation confirmation.

Costs Nobody Warns You About

This is the section that causes the most surprise. Registration itself is not expensive. The ongoing costs are what gets people.

Year 1 estimates for a newly registered eenmanszaak:

Ondernemingsloket registration fee: around €80-€120 one-time
Social contributions (jaar 1-3 voorlopige bijdragen): approximately €900/quarter, totalling ~€3,600/year for starters. This is calculated as a flat rate for the first three years, then regularised based on your actual net income. If you earn more than the threshold, you'll get a regularisation bill later. If you earn less, you get a refund. The timing of the regularisation is typically 2-3 years behind, meaning you can get a surprise bill in year 3 based on your year 1 earnings.
Accountant fees: €100-€250/month for a basic eenmanszaak with regular invoicing. Non-negotiable in my view (see below).
Business insurance / professional liability (BA beroepsaansprakelijkheid): €400-€800/year depending on your activity and coverage. Less critical if you work through contracts with limitation clauses, more critical if you're touching anything financial or safety-critical.
Tools and subscriptions: Not unique to Belgium, but don't forget these when calculating your effective take-home rate.

The real cost of independence is not what you pay when you register. It's the quarterly cash flow discipline required to have your social contributions and taxes ready when due.

The Accountant Question

Get an accountant. I know you're a developer and you think you can handle it. You probably can, technically. But the time you spend on quarterly VAT declarations, annual income calculations, investment deduction optimization, and regularisation correspondence is time you're not billing or building. The math doesn't work in your favor.

How to find a good one:

Ask other freelancers in your network. In-person referrals are the most reliable.
Look for an accountant who specifically handles zelfstandigen or vrije beroepen (freelancers and independent workers). They know the patterns and won't waste your time explaining what an eenmanszaak is.
Check that they use modern accounting software (Exact Online, Octopus, Accountable) and can integrate with your bank exports.
Ask upfront about their communication style: do they prefer email, WhatsApp, a portal? Will they proactively flag things, or wait for you to ask?

I went through two accountants before finding one that worked. The first was too slow (days to answer basic questions). The second had great tools but didn't understand software consulting at all. The third, who I've stayed with, charges a bit more but has saved me far more than the difference in tax planning alone.

The Tax Reality

As an eenmanszaak, your business profit flows directly into your personal income tax return. Belgium has progressive personal income tax rates, starting at 25% and reaching 50% above a threshold (currently around €46,440/year net taxable income). There's no flat corporate tax rate for eenmanszaak.

What this means practically:

If you earn €100,000 in consulting revenue, after social contributions (~€15,000-€20,000) and deductible expenses, you might have €70,000-€80,000 of net business income, taxed at the top marginal rates
Effective all-in tax rate for a well-earning eenmanszaak is typically in the 40-55% range
Investment deductions (investeringsaftrek) let you deduct 20-25% of qualifying business investments on top of normal depreciation. Worthwhile if you're buying hardware, software licenses, or other capital equipment.
Quarterly prepayment of taxes (voorafbetaling) reduces penalties and smooths cash flow; your accountant will tell you when and how much

The BVBA/BV (private limited company) becomes financially attractive above roughly €50,000-€60,000 in net annual profit because of lower corporate tax rates and the ability to manage remuneration between salary and dividends. Below that, the administrative overhead of a BVBA (notary fees, company secretary, annual accounts filing) outweighs the tax benefit.

Was It Worth It?

Yes. Unambiguously.

The bureaucratic overhead is real but finite. It's mostly front-loaded in the first year while you're learning the system. After that, it's quarterly rhythm: check in with accountant, file VAT, pay social contributions, move on.

The independence is harder to put a number on. I set my rates based on the value I provide, not on what a job listing says. I pick my clients. I work on my own products without asking permission. I can take a week to think without explaining it to a manager.

For developers specifically: the Belgian market has consistent demand for technical consulting. Companies of all sizes regularly need short-term senior technical help for architecture reviews, greenfield build-outs, and legacy modernisation. The rate you can command as an experienced independent developer in Belgium is meaningfully higher than what most companies pay salaried equivalents.

Advice for Developers Considering It

Don't wait for the perfect moment. There isn't one. If you have a client lined up or a realistic path to one within 90 days, register.
Set aside 35-40% of every invoice immediately, before you touch it. Social contributions, taxes, and accountant fees will claim it. The rest is actually yours.
Negotiate contracts, not just rates. Payment terms, liability caps, IP ownership clauses. These matter more over time than an extra €25/hour.
Track everything from day one. Expenses, invoices, client communications. The cost of retroactive organisation is higher than the cost of real-time tracking.
Register your NACE codes broadly. It's easier to add descriptions to an existing registration than to change them later.

The eenmanszaak is the right starting structure for most developers going independent in Belgium. It's simple, fast to set up, and more than sufficient for consulting work. Graduate to a BV when the numbers justify it. Your accountant will tell you when you're there.